Chemical dehumidifying system



Feb. 17, 1942. A. B. NEwToN v 2,273,804..

l CHEMICAL DEHUMIDIFYING sYsTEM- l Filed Jan. 25, 19:59

" fforngg intimal Feb. 17, 1942 2,213,801 CHEMICAL nEHUMmmmG SYSTEM Alwin B. Newton, Minneapolis, Minn., assignor to Minneapolis-Honeywell Regulator Company,

Minneapolis,

Minn., a corporation of Delaware r Application January 23, 1939, serial No. 252,378

2 Claims.

This invention relates to a chemical dehumidifying system and more particularly to a controll system therefor.

In dehumidifying air by the use of a solution of a hygroscopic salt, such as lithium chloride, or calcium chloride, it is customary to spray the solution in a stream of air to be dehumidlfled, and the moisture of the airisabsorbed by the of to vcontrol the reactivating means. A sample of the solution whose concentration is to be controlled is passed through a. small boiler to which heat is constantly applied, anda device which responds to the boiling point of the solution in this boiler is arranged to control the reactivating solution, thus lowering the humidity of the air and at the same time reducing the concentration of the hygroscopic solution. In order that the solution may be used over and over again, it is necessary to drive off the moisture which is absorbed thereby, in order that the solution may be maintained suiliciently concentrated to effect the necessary dehumidicatlon of the air, since as the solution becomes less concentrated, its power of absorbing the moisture in the air decreases. The reactivation of the solution should be carefully controlled, since if, too much moisture is driven from the solution, the resulting `high concentration thereof may result in crystallization of the salt in the solution.

One method that has been used for controlling the reactivation of the hygroscopic solution is by measuring the density of the solution, which varies in accordance vwith the concentration thereof, and controlling the amount of reactivation in accordance with the density. The density is measured'by means of a hydrometer, but inasmuch as the concentration, or the vapor absorbin'g characteristics vary greatly with very small changes in the density, it has been found very diicult to accurately control the 'reactivation by this means. Another method which has beenproposed to measure the concentration and control the reactivation is by separating a sample of the solution whose concentration is to`be measured and controlled from a weak solution of known concentration, which may be pure water, by an osmotic wall, and controlling the reactivation in accordance with the rate of flow through the wall, which will vary in accordance with the relative densities of the solution. Such a system is Illustrated in the application of Raymond P. Mattern and William L. McGrath, Serial No. 198.986, filed March 30, 1938.

In accordance with my invention, the changesI in concentration are measured by a relatively simple arrangement and one which respondsv rapidly to such changes, and the reactivatng means is in turn controlled thereby. 'I'he boiling point of the solution varies in accordance with the hygroscopic solution to be means in a manner to maintain the boiling point thereof substantially constant, which in turn causes the concentration .of the main body of maintained substantially constant.

It is therefore an object of 'my invention to provide a novel control arrangement for controlling the reactivation of a hygroscopic fluid used in a chemical dehumidifying system.

More particularly it is an object of my invention to control the vreactivation of a hygroscopic solution by controlling the amount of the reactivation in accordance with the boiling point thereof.

Other objects and advantages will become apparent upon a study of the specification, claims, and appended drawing wherein is illustrated a preferred form of my invention.

Referring more particularly to the drawing, an air conditioning chamber is represented by the reference character Ill, this chamber including an inlet II and an outlet I2. A fan I3 is 'illustrated as being located at the upper portion of the chamber, this fan being driven by a suitable motor I4 and is provided to cause a circulation of air upwardly through the chamber III.

The outlet I2 may Vcommunicate with a space being conditioned and the inlet II may also communicate with'the space or may communicate with a source'of fresh air or if desired, a mixture of fresh and return air may circulate through the inlet II in a manner Well known in the art.

Located adjacent the upper end of the chamber Ill is a spray I5 through which a hygroscopic fluid mayissue, this spray contacting the upwardly flowing stream of air and removing a certain amount of moisture therefrom, thus lowering the relative humidity of the air.A A pump I6 having an inlet connected by a pipe I"I to the interior of the tank I8 is provided for supplying iluid to the spray I5, the outlet of the pump I6 being connected to the spray by means of the pipes I9 and 20. The hygroscopic fluid is returned to the tank I8 by means of `a pipe 2|.

Inasmuch as the hygroscopicl fluid absorbs water from the air passing through the chamber I0, the concentration of the fluid returning to the tank I8 will be less than the uid in thel the concentration, and this property is availed J5 tank and accordinglyit is necessary to drive oil this excess moisture from the hygroscopic fluid so as to maintain the concentration of the iluid in the tank I8 at a substantially constant value so that moisture absorbing property will be substantially constant during operation of the system. For this purpose a regenerating means is provided, this regenerating means including a heater represented by the reference character 25. The pump I6, besides supplying fluid to the spray I5, also supplies uid to the coil 25 located in the heater 25 by means of the pipes I9 and 21. A pipe 23 controlled by a suitable valve 29 is provided for supplying a suitable heating medium to the heater 25, which heating medium may be in the form of steam or any other suitable heating medium, the heating medium leaving the heater by way of the pipe 33. It should be understood that the heater 25 may be heated by gas, electricity, or in any suitablemanner. The temperature of the iluid leaving the heater 25 will depend upon the amount of the heating medium supplied thereto and consequently will depend upon the opening of the valve 29 and consequently the temperature of the uid leaving the heater is readily controlled.

The upper portion of the coil 26 communicates by means of a pipe 30 with a spray 3| located within a chamber 32 through which air is caused to flow upwardly by means of the fan 33 driven by the motor 34. The uid leaving the spray 3l will be at a relatively high temperature and consequently the hygroscopic fluid which may be in the form of lithium chloride solution or a calcium chloride solution will be unable to absorb moisture from the air since the moisture absorbing properties of such solutions decrease as the .temperature thereof in' creases. Instead of absorbing moisture from the air the solution will be suillciently hot so that the air passing through the chamber 32 will absorb moisture from the heated solution and in this manner the concentration of the solution is increased. Located-below the chamber; 32 is a .tank 36 which collects the now concentrated hygroscopic solution and delivers it by way of a pipe 21, a heat exchanger 33, and a cooler 29 back to the tank I3. The heat exchanger 33 is provided for preheating the solution being -delivered to the heater 25 and for precooling the concentrated solution being delivered back to the tank I3. The cooler is provided for further reducing the temperature of the solution to the proper value and for this purpose' a cooling medium may be supplied thereto by means of a pipe43'contro1led by. a valve 4I, the cooling medium leaving the cooler by way of the pipe 42. While the valve 4I has been shown as being manually controlled, it will be understood that if desired this valve may be automatically controlled in any well known manner to maintain the temperature of the solution in the tank I3 at a desired value, but since this forms no part of the present invention such a control means has not been illustrated. It will be apparent that a suitablywcontrolled refrigeration system may be employed for controlling the temperature of the solution in the tank I3.

It will now be understood that the reactivating system controls the concentration of the solution in the tank I3' and the concentration of this solution, may be varied by varying the -opening of the valve 29 since this valve controls thereby to the air or in other words, the amount of moisture removed from the solution. In order to control the position of the valve 29, use is made of the fact that the boiling point thereof varies in accordance with the concentration of the solution.

The reference character 50 .illustrates a small boiler to which a small amount of the solution in the ytank i8 is fed by the pump I5 and the pipe 5I, the ow through which may be controlled by the valve 52. The outlet ofthe valve 52 communicates by means of the pipe 53 with a heat exchanger 54 which communicates with the boiler 50 at a position remote from the bottom thereof as illustrated in the drawing. It will be understood that this boiler is of very small size compared with the heater 25 and that the amount of solution supplied to this boiler is considerably less than is supplied to the heater 25. Heating means which may take the form of a burner 55 located below the boiler is provided for causing the solution within the boiler 5II to be maintained in a state of boiling at all times during operation of the system. A valve 51 is located in the fuel supply pipe to the burner 55 for controlling the supply of fuel thereto and this valve may be automatically controlled in a manner to be described. A small pipe 59 connected to the supply side of the valve 51 supplies gas to a constantly burning pilot for igniting the gas issuing from the main burner l vto be maintained constant, this overilow pipe passing within the heat exchanger 54 to the lower part of the air conditioning chamber III so that any liquid that passes through this overflow pipe willybe eiIective for preheating the uid being supplied to the boiler, the iluid passing through the pipe 53 at the same time being cooled and then passing back to the tank I3 by means of the pipe 2l. The evaporated solution will pass from the upper portion of the boiler through the pipe 30 to the air conditioning chamber- III where it will be condensed by the cool solution being sprayed from the spray I5 so that thisevaporated solution will pass back to the tank I3. A pipe 5I controlled by a valve 52 connects the lower portion of the boiler with the overilow pipe 53 so that the boiler may be drained of the solution at any time if desired. Located within the solution in the boiler 53 is a bulb 55 communicating by means'of a capillarytube 55 with a bellows 51, the tube, bulb. and bellows being provided with a suitable volatile ll so that the bellows 51 will expand and contract in accordance with variations in temperature in the upper portion of the boiler. Pivoted at 53 is a lever having an arm 59 biased by means of a spring 10 into engagement with the upper portion of the bellows, this lever also including a second arm 1I which forms the slider arm of a potentiometer including the resistance 1 decreases the arm 1I will move in the opposite4 direction over the resistance 12.

Located in the pipe so between the Smau boiler 50 and the air conditioning chamber I0 "is a, pivoted vane 53 which controls the position of a' mercury switch 54 provided with terminals 3 5, 35,1" 31, and 33. When there is a flow of steam-V through the pipe 50 the vane 53 assumes the position and the mercury switch 64 will be tilted in the opposite direction wherein the terminals 81 and 88 are connected together.

Controlled by the potentiometer 12 and the switch 64 is a motor 15 which includes an arm 16 connected by means of a link 11 to the stem 18 l of the valve 29. The motor may be a proportioning motor of the type illustrated in the patent to D. G. Taylor, No. 2,028,110 issued January 14, 1936. 'I'he extremities of the resistance 12 are connected by means of conductors 80 and 8| to the outer terminals of the motor 15. When the system is in operation and steam is owing through the pipe 60 the mercury switch 64 will be in the position illustrated and in this position thereof the slider 1I is connected by means of the conductor 89, terminals 85 and 86 ofthe switch 64, and conductor 82 to the center terminal of the motor 15 so that when steam is flowing through the pipe 60, the motor 15 is controlled directly 'bythe potentiometer 12 or Ain other words, in accordance with the temperature of the solution in the boiler 50. Power may be supplied to the motor by means of conductors 83 and 84 connected to any suitable source of power (not shown). As the concentration of the solution in the boiler 50 decreases, the boiling point of the solution, if the solution be lithium chloride or calcium'chloride for example,l will also decrease and accordingly the temperature of the evaporated solution affecting the bulb 65 will s decrease and the slider arm 1I will move towards the left. This movement of the slider arm over the potentiometer will cause operation of the motor 15 to move the valve 29 towards wide open position by an amountwhich is proportional to the decrease in the boiling point of the solution in the boiler 50 or in other words, in accordance with the decrease of the concentration ofthe solution in the boiler 50 which is being f ed dlrectly from the tank |8. It will accordingly be seen that as the solution in the tank I8 becomes more dilute, more heat is supplied to the reactivatlng system, the temperature of the spray 3| increases, and more moisture is given up to the air passing through the chamber 32 by the hygroscopic. fluid and in this manner the concentration of the solution in the tank I8 may-be effectively controlled.

Should the concentration of the solution in the tank 8 become so high that no reactivation thereof is' necessary, the boiling point will also become high and the valve 29 will be moved to a closed or minimum position thus reducing to a minimum the amount of heating medium being supplied to the heater 25 by means of a pipe 28. At this time it is unnecessary to circulate any of the solution through the heater I8 or to operate the fan 33 for drawing air upwardly through the chamber 32. Accordingly a mercury switch 90 is carried by an extension 9| of the arm 16 and this `switch is moved to open position when the valve 93 which may be in the `form of a solenoid for causing movement of the valve 92 -to open position when the motor 93 is energized. The switch also controls the operation of the motor 34 which drives the fan 33, this switch when in closed position, las illustrated, causing energize.- tion of the valve motor 93 and the fan motor 34. Line wires 95 and 96^are provided for'supplying power to these motors, these wires being connected to a suitable source of power (not shown). With the switch 90 in -the fposition illustrated, power is supplied to the fan motor 34 as follows: from the line wire 96 through the switch 90, conductors 98, 99, fan motor 34 and conductor |00 to the line wire 95. Power is also supplied at this time to the valve motor 93 as follows: from the une wire 96 through the switch su, conductors 98, IOI,'valve motor 93 and conductor |02 to the line wire 95. It will now be 'apparent that as long as the valve 29 is in open position and switch 90 is in its closed position as illustrated, the fan 35L will operate to cause a Ailow of air upwardly through the chamber 32 and the valve 92 will be opened to permit a circulation of hygroscopic fluid through the coil 26 in the heater 25 to the spray 3|. As soon as the valve 29 becomes closed however, then switch 90 moves to its circuit breaking position thus deenergizing the fan motor 34 and the valve motor 93, thus stopping the fan 33 and causing the valve 94 to move to closed position` under the influence of gravity or any suitable biasing means (not shown).

Located within the space being conditioned is a humidity responsive element ||5 controlling thev position of a lever II6 pivoted at I|1, there being a spring I|8 connected to the lever II6 and tending to move the lever in aposition to cause elongation of the humidity responsive element II5. 'I'he arm |I6 cooperates with a contact |20 and upon an increase in humidity in the spacev the arm I|6 will be moved downwardly out of engagement with the contact |20 by the spring II8 by reason of the elongation of the humidity responsive element |I5. This humidity responsive device controls the energization of a relay |25, which relay comprises a coil |26 having an armature |21 `which controls the position of the switch arm |28 which in turn cooperates with a fixed contact |29. Energization of the coil |26` causes movement of the arm |28 into engagement with the contact |29 and upon deenergization of the relay coil the arm |28 moves out of engagement therewith under 'the influence of gravity or any suitable biasing means (not shown). Power may be supplied to the relay |26 by means of the step-down transformer |30 comprising a low tension secondary I3I and a high tension primary |32 connected `to the Aline wires |33 and |34 connected toa suitable source of power (not shown). When the humidity in the space is high, the arm I I6 `of the humidity responsive device will be in engagement with the contact |20, as illustrated, and the relay coil |26 will be energized as follows: from one side of the transformer secondary I3| through conductor |35, contact 20, switch arm |I6, conductor |36, relay coil |26, and conductor |31 to the other side of the secondary I3|.

The relay |25 controls the energization of the pump I6 and the motor |40 which may be in the form of a solenoid which inl turn controls the position of the valve 51 for controlling the supply" of gas to the main burner 56. Power is supplied`to the pump I6 when the relay |25 is energized as follows: from the line |33 throughy conductor |42, the pump I6, conductor |43,

switch arm |28, contact |29, and conductor |44 to the line wire |84. At the same time power is supplied to the solenoid or valve motor |40 as follows: from line wire |93 -through conductors |42, |46, solenoid |40, conductors |41, |48, switch arm |28, contact |29, and conductor |44 to the line wire |34. It will thus be seen that as long as the humidity in the space is'too highand there is a need for dehumidiflcation the relay |25 is energized thus causing the pump I5 to operate and energizing the solenoid |40 to open the fuel supply valve 51 which controls the supply of fuel to the burner 56.

As soon as the humidity in the space drops to the desired value a circuit to the. relay |25 is opened at the contact |20 thus deenergizing the pump I8 and the solenoid |40. The valve 51 now 1moves to closed position under the influence of As the temperature of the solution in the boiler decreases, however, there will be a tendency for the valve 29 to be opened thus increasing the supply of steam tothe regenerator 25. However, upon the cooling of the solution in the boiler 50, steam will no longer iiow through the pipe 50 and the vane 63 will thus move'downwardlyv and cause the mercury switch 84 to be tilted in the opposite direction. When this happens, the'connection between the slider arm 1| and the center terminal of the motor is interrupted at the switch terminal 85 but the center and left hand terminals of the motor are directly connected together at this time by means of the following circuit: from the center terminal of the motor through conductor 82, switch terminals 81 and 88, and conductors 91 and 80 to the left hand terminal of the motor. The result of this is to cause the motor 15 to move the valve 29 to its entirely closed position so that heat is no longer supplied to the heater 25. At the same time the mercury switch 90 is tilted to open position which causes the fan motor 34 to be deenergized since it is not necessary at this time to draw air through the cooling tower 84. The system 'is now entirely shut down and will remain so until there is another call for dehumidication whereupon the pump I8 will be again placed into operation and the valve 51 will be lopened thus causing the boiler 50 to heat up and steam to be generated therein, -'1 'he slider 1| of the control potentiometer will assume a position correspond-v ing to the temperature of thesolution in the boiler and after steam starts to generate, the vane 83 will tilt back to the position shown thus placing the regenerating system in operation and tank I8. Also while I have shown my invention as being automatically controlled it will be. obvious that the principles of my invention are 'applicable to a system which might be manually controlled by observing the boiling temperature of the solution in the boiler 50 and manually adjusting the valve 29 inaccordance with this temperature. For this purpose suitable indicia ||0 may be provided for cooperation with the arm 1| to indicate the boiling temperature of the solution in the boiler 50.

It will now be understood that I have provided a relatively simple system for controlling the concentration of a solution by controlling the reactivation of the solution in accordance with the boiling temperature thereof and since the boiling temperatures of the solutions vary for varying concentrations over a wider range than the densities thereof, it is possible to more accurately control the concentration and the humidity absorbing power thereof than in prior systems wherein the reactivation is controlled directly in response to variations in the density of the solution. While my invention has been embodied in a dehumidifying system, it should be understood that the principles thereof are applicable to other systems wherein the concentration of a solution is to be controlled.

Many other modifications may 'also become apparent to those skilled in the -art and I therefore desire to be limited only by the scope of the appended claims.

Iclaim as my invention:

1. In a system for controlling the concentration of a solution having a boiling point which varies with its concentration, the combination an amount of moisture from the solution to the air depending upon the temperature of the solution, regulating means for regulating the heating effect of said heater and hence the concentrating eil'ect of saidconcentrator, a boiler sepaboiler, means to heat the boiler sunlciently to boil the solution therein whatever its concentration may be, and means responsive to the concentration of the solution in the boiler comprising a thermostat responsive to the boiling temperature ofthe solution in the boiler for controlling causing the proper -amount of heating medium to be'supplied to the heater 25.

While I have described my invention more particularly with reference to the use of hygroscopic solutions of the lithium chloride or calcium chloride variety it will be obvious that any type of hygroscopic solution may be employed. With certain types of hygroscopic solutions, the boiling point decreases as the concentration increases and if solutions of this character are used then the motor 15 will be operated to move the valve 29 towards closed position as the boiling point of the solution decreases which would indicate an increase in concentration ofthe solution in the the regulating means to cause heating of the solution to a temperature such that its subsequent contact with air will liberate the amount of moisture necessary for the solution to return the concentration of the solution to the desired value.

2. In a system for controlling the concentration of a solution, the combination of, a concenn ALWIN B. NEWTON. 

